1. Preheat oven to 400°.
2. Arrange asparagus in a single layer on baking sheet; coat with cooking spray. Sprinkle with salt and pepper. Bake at 400° for 12 minutes or until tender.
3. Melt the butter in a small skillet over medium heat; cook for 3 minutes or until lightly browned, shaking pan occasionally. Remove from heat; stir in soy sauce and vinegar. Drizzle over asparagus, tossing well to coat. Serve immediately.
Finish the asparagus just before serving dinner. Cooking the butter until it browns slightly gives the dish a nutty flavor; watch carefully, though, since it can burn easily.